At present, conventional edge emitting semiconductor lasers play a significant role in optical communication due to their high operating efficiency and modulation capabilities, however, edge emitting semiconductor lasers have several shortcomings or problems, thus making them difficult to use in many applications.
Recently, there has been an increased interest in vertical cavity surface emitting lasers (VCSELs). The conventional VCSEL has several advantages, such as emitting light perpendicular to the surface of the die, and the possibility of fabrication of two dimensional arrays. However, while conventional VCSELs have several advantages, they also have several disadvantages with regard to emission in the infra-red spectrum longer than 1 .mu.m primarily due to the poor reflectivity of the distributed Bragg reflectors which are contained as a part of the VCSEL structure. Because of this, manufacturability of VCSELs for the infra-red spectrum longer than 1 .mu.m is severely limited.
Long wavelength (1.32 micrometers to 1.55 micrometers) vertical cavity surface emitting lasers (VCSELs) are of great interest in the optical telecommunications industry because of the minimum fiber dispersion at 1.32 micrometers and the minimum fiber loss at 1.55 micrometers. The dispersion shifted fiber will have both the minimum dispersion and the minimum loss at 1.55 micrometers. The long wavelength VCSEL is based on an In.sub.x Ga.sub.1-x As.sub.y P.sub.1-y active layer lattice matched to InP cladding layers. However, in this system, it is practically impossible to achieve a suitable monolithic DBR based mirror structure because of the insignificant difference in the refractive indices in this material system. As a result, many layers, or mirror pairs, are needed in order to achieve decent reflectivity.
Many attempts have been made to address this problem, including fabrication of devices that utilize wafer bonding techniques, yet only limited success has been shown. As an example, devices are currently utilized in which a DBR mirror structure is grown on a GaAs substrate. Next, the active layer is grown on the InP substrate. The two elements are then flipped mounted together and fused using wafer fusion techniques. The end result is a device that is expensive to manufacture, exhibits low efficiency, low output power and low yield. In addition, the interface defect density in the wafer fusion procedure causes potential reliability problems of the VCSEL end product.
Thus, there is a need for developing a reliable and cost effective infra-red vertical cavity surface emitting laser (VCSEL) for use in optical telecommunications technologies.
Accordingly, it is highly desirable to provide for an infra-red vertical cavity surface emitting laser (VCSEL) for use in optical telecommunications technologies that includes the fabrication of an InGaAsP/InP material based active region of a VCSEL structure on a silicon substrate, having included as a part thereof a DBR mirror structure composed of alternating layers of a silicon (Si) material and a silicon oxide (SiO.sub.2) material, fused to the InGaAsP/InP active region using wafer fusion techniques, thereby allowing for a high degree of reflectivity.
It is a purpose of the present invention to provide a new and improved vertical cavity surface emitting laser (VCSEL) that utilizes a silicon substrate, and an InGaAsP/InP material based active region, thereby achieving a high degree of reflectivity.
It is a further purpose of the present invention to provide for a vertical cavity surface emitting laser that includes a silicon substrate having formed thereon alternating layers of silicon (Si) and silicon dioxide (SiO.sub.2), as part of a highly reflective DBR mirror structure included within the VCSEL device.
It is a further purpose of the present invention to provide for a new and improved vertical cavity surface emitting laser (VCSEL) which will result in less defect density at the fused interface of the DBR mirror and the InGaAsP/InP active region.
It is a still further purpose of the present invention to provide for a new and improved vertical cavity surface emitting laser that is capable of emission in the infra-red spectrum.